arXiv subjects

A. V. Gurevich

Publications and source records attributed to A. V. Gurevich.

9 recordsLinked to original sources

arXiv2007

Lagrangian structure functions in fully-developed hydrodynamical turbulence

The Lagrangian velocity structure functions in the inertial range of fully developed fluid turbulence are derived basing on the Navier-Stokes equations. For time $τ$ much smaller than the correlation time, the structure functions are shown to obey the scaling relations $K_n(τ)\propto τ^{ζ_n}$. The scaling exponents $ζ_n$ are calculated analytically. The obtained values are in amazing agreement with the unique experimental results of the Bodenschatz group \cite{Bod2}. New notion -- the Lagrangian position structure functions $R_n(τ)$ is introduced. All the $R_n$ of the order $n>3$ are shown to have a universal scaling.

physics.flu-dyn↗

arXiv2006

Generation of small-scale structures in the developed turbulence

The Navier-Stokes equation for incompressible liquid is considered in the limit of infinitely large Reynolds number. It is assumed that the flow instability leads to generation of steady-state large-scale pulsations. The excitation and evolution of the small-scale turbulence is investigated. It is shown that the developed small-scale pulsations are intermittent. The maximal amplitude of the vorticity fluctuations is reached along the vortex filaments. Basing on the obtained solution, the pair correlation function in the limit $r\to 0$ is calculated. It is shown that the function obeys the Kolmogorov law $r^{2/3}$.

physics.flu-dyn↗

arXiv2004

High energy cosmic ray particles and the most powerful new type discharges in thunderstorm atmosphere

The runaway breakdown -- extensive atmospheric shower discharge (RB - EAS) excited in thunderstorm atmosphere by high energy cosmic ray particles ($ε_p>10^{17} - 10^{19}$ eV) generate very powerful radio pulse. The RB - EAS theory is compared with observations of radio pulses. An agreement between the theory and experiment is established. The existence of nowaday satellite and ground based systems which obtain regularly a large amount of observational radio data could allow to use them in combination with other methods for effective study of high energy cosmic ray particles

hep-ex↗

arXiv2004

The growth of supermassive black holes in the centers of galaxies: absorption of stars and activity of galactic nuclei

The evolution of a supermassive black hole in the center of galaxy is considered. We analyze the kinetic equation describing relaxation processes associated with stellar encounters. The initial distribution function of stars is assumed to be isothermal, and it changes in accordance with consumption of stars by the black hole. We calculate the consumption rate and obtain the law of growth of supermassive black hole, i.e. the dependence of the black hole mass on time and on the velocity dispersion of stars. The obtained values of mean black hole mass and mean rate of stars consumption by a black hole are in reasonable agreement with observational data.

astro-ph↗

arXiv2004

Experimental Evidence of Giant Electron - Gamma Bursts Generated by Extensive Atmospheric Showers in Thunderclouds

The existence of a new phenomena - giant electron-gamma bursts is established. The bursts are generated in thunderclouds as a result of the combined action of runaway breakdown and extensive atmosphere showers (RB-EAS). The experiments were fulfilled at the Tien Shan Mountain Scientific Station using EAS-Radio installation. This specially constructed installation consists of a wide spread EAS trigger array and a high time resolution radiointerferometer.

hep-ex↗

arXiv2003

Dark matter in galaxies and growth of giant black holes

The connection between dark matter and giant black holes in the galactic nuclei is investigated. The joint evolution of dark and luminous matter in averaged self-consistent gravitational potential is considered. It is shown that the distribution of dark matter remains spherically symmetric even in presence of essential asymmetry of luminous matter in the galaxy. The kinetic equation describing evolution of dark matter particles distribution function which takes into account their dynamics in gravitational potential and scattering on stars is derived. It is shown that significant flux of dark matter on a seed black hole in the center of galaxy should appear. The growth law of seed black hole due to absorption of dark matter is derived. It appears that during the lifetime of galaxy the seed black hole should grow significantly, up to observed value. Brief analysis of observational data shows that the presented theory is in reasonable agreement with observations.

astro-ph↗

arXiv1998

Small-scale structure of dark matter and microlensing

It has been revealed using microlensing that a considerable part, possibly more than half, of the dark matter in the halo of our Galaxy consists of objects with a mass spectrum ranging from 0.05 to 0.8 of the solar mass. What is the nature of these objects? There exist two hypotheses. According to one, these are Jupiter type planets or small stars (brown and white dwarfs) consisting of normal baryonic matter. According to the other, these are non-compact objects, i.e., small-scale formations in non-baryonic dark matter. Here, a theory is proposed describing the possibility of the existence of non-compact objects in the halo of our Galaxy, their structure and formation from non-baryonic matter. The theory of microlensing on compact and non-compact objects is considered in detail. The results of microlensing observations are described and compared with theory. Possible astrophysical manifestations of the presence of small-scale structure are pointed out. The field is being extensively studied and is of fundamental interest for cosmology and astrophysics.

astro-ph↗

arXiv1997

MACHO halo objects as sources of gamma bursts

A new model of gamma bursts (GB) generated by MACHO's in the form of noncompact dark matter halo objects (NO) is proposed. The model explain well the spherical symmetry, $log N - log S$ curve of GB absolutely identically to the well-known giant dark matter halo (GDMH) model. The main difficulty of GDMH model -- the lack of neutron stars in our galactic halo is eliminated because of the large number of NO ($\sim 10^{13}$) which is quite close to a total number of bursts during the life time of the Universe. The proposed mechanism of the burst is the instability and explosion of the baryonic core (BC) of NO. The structure of BC and possible mechanism of BC explosion are discussed. The intensive infrared emission from BC of neutralino stars (NeS) at the wavelength $(3 - 8)μ$ is predicted. The possibility to discover NeS by observation of infrared emission from the recently distinguished point-like gamma sources is indicated.

astro-ph↗

arXiv1997

Gamma Radiation by Neutralino Stars

A new model of gamma radiation (GR) generated by neutralino annihilation in neutralino stars (NeS) is proposed. Diffuse Galactic and extragalactic GR is calculated for this model and is shown to be in a reasonable agreement with observations. The point source component (P) is picked out among nonidentified discrete gamma sources from EGRET catalog. This component is shown to be distributed isotropically and homogeneously, as it should be for NeS. Gamma radiation from significant part of P-sources is supposed to be the direct radiation from individual NeS. This supposition is shown to be in agreement with observations. The comparison of the theory with observed GR gives a possibility to establish some important features of CDM particle.

astro-ph↗